When data stored on a data storage medium is compromised (i.e., corrupted or lost), a data recovery scheme may be deployed to reconstruct or restore the compromised data. Data restoration is one way of recovering data and typically requires restoring or rebuilding more than just the compromised data (e.g., requires restoring an entire volume of data) from a backup medium. Restoration may not be most efficient if backed up data is retrieved from storage media that is remote or comparatively slow or if restoration from backup storage requires restoring more than just the data that has been compromised. For example, to restore five bytes of compromised data, 500 megabytes of backed up data may have to be restored.
A more efficient data recovery scheme may be designed based on a redundancy mechanism which creates extra resiliency by duplicating or adding parity to data stored on relatively fast storage media that are readily and locally available. This is in contrast data recovery from slower and remotely located storage media that is typically used for data restoration from backup media. Without going into a high level of detail, in a redundant system, the corrupted or lost data is generally reconstructed based on metadata and redundancy factors built in the system, quickly and without the delays associated with having to restore a large volume of data from a backup storage medium. This means that data reconstruction using a redundancy mechanism may be achieved in a fraction of the time as it would take to restore the data from a backup system.
Data backup is important for disaster recovery in case the data redundancy mechanism is unable to reconstruct lost or corrupted data. Since data backup takes place periodically, data that is written or updated after the latest backup process has no copies in the backup storage. Thus, newly written or updated data is most vulnerable if the redundancy mechanism fails. That is, the newly updated data can neither be reconstructed from a failed redundancy mechanism nor can it be restored from the backup media. Even if the redundancy mechanism is functional, during the time period in which the data is being reconstructed, only one copy of the data exists. As reconstruction time grows, the window of exposure grows. As disk volume grows, the quantity of data exposed grows.